Process for simultaneous dimerization and reduction



mononitriles and more particularly process for the preparation of adipo'nitrlle by Patented Apr. 6, 1948 1 PROCESS FOR SIMULTA NEOUS DIMERIZA- TION AND REDUCTION Robert M. Leekley, Chicago, 11]., assilnor to E. I. du Pont de Nemours a Company, Wilmington, Del., a corporation of Delaware No Drawing. Application July 18, 1946.

Serial No. 684,547

8 Claims. (Cl. 260-4653) 1 n This invention relates to a process for the preparation of saturated aliphatic dinitriles from alpha, beta-ethylenically unsaturated aliphatic to a catalytic the reductive dimerization of acrylonitrile.

Although it is well known that ce tain alpha, 1

beta-unsaturated compounds, such as he acrylates, methacrylates, acrolein, and methylvinylketone, can be dimerized under certain conditions to yield unsaturated dimeric pigducts, the simultaneous dimerization and reduction oi such compounds to yield saturated products has heretofore never been accomplished. For example, the U. S. patent to Howk 2,232,785, issued February 25, 1941, shows the dimerization of acrylo-I nitrile by heating in the presence of an inhibitor at a temperature of 200 C. However, an unsaturated dinitrile is produced which on subsequent hydrogenation and hydrolysis yields a dicarboxylic acid'which is stated to be presumably methyl In the preparation of adiponitrile from acrylon-itrile there should be used essentially" molar equivalent amounts of elemental magnesium and acrylonitrile in an inert solvent, such as benzene. These reactants are placed in a suitable reaction vessel along with the mercuric chloride and the mixture refluxed with stirring. To this mixture is added an amount of a low molecular weight primary aliphatic monohydric alcohol I which is more than suflicient to react with all the magnesium and at such a rate as to generate a continuous but slow evolution of hydrogen. After reaction is complete, the adiponitrile is islolated by fractional distillation or other means known to the art;

Although the preferred method for effecting the simultaneous reductive dimerization of alpha, beta-ethylenicaliy unsaturated mononitriles to saturated dinitriles is through the use of glutaric acid. Thus, thermal dimerization of acrylonitrile in the presence of inhibitors has produced branched chain unsaturated dimersbut not a linear saturated dimer such as adiponitrile.

It is an object of this invention to provide a new process for the preparation of linear saturated aliphatic dinitriles from alpha, betaethylenioally unsaturated aliphatic mononitrlles. A further object of thisinvention is the provision of a process for the preparation of linear saturated aliphatic dinitriles from alpha, betaethylenically unsaturated aliphatic mononitriles in one stage. A still further object is to provide an economical process for producing adiponitrile from acrylonitrile. Other objects will appearv hereinafter.

These objects are accomplished by the follow- 5 ing invention of a process for the preparation of a linear saturated aliphatic dinitrile from an alpha, beta-ethylenically unsaturated aliphatic mononitrile which comprises treating the said alpha, beta-ethylenically unsaturated aliphatic mononitrile with active hydrogen, formed by reacting magnesium or a magnesium alloy with a primary aliphatic monohydric alcohol, in the presence of magnesium or magnesium alloy and a promoter, such as mercuric chloride. Thus, acrylonitrile is simultaneously dimerized and reduced to adiponitrile by treating with active hy cirogen, formed by reacting a primary aliphatic monohydric alcohol with magnesium in thepresence of magnesium and a small amount of mercuric chloride as a promoter.

magnesium, or one of its alloys, in conjunction with a lower primary aliphatic monohydric alcohol and mercuric chloride, an alternative method for efiecting this reaction is through the employ. ment of magnesium, or an 'organomagnesium compound, such as an alcoholate, incombination with hydrogen and a hydrogenation catalyst, such as nickel.

By alpha, beta-ethylenically unsaturated aliphatic mononitrile as used herein is meant a mononitrile in which the nitrile (-CN) group is attached directly to a carbon atom in the aliphatic chain, which carbon atom is in turn attached to another carbon atom by an eth'ylenic double bond.

By lower primary aliphatic monohydric alcohol as used herein, is meant a primary aliphatic monohydric alcohol having one to five cerbon atoms, such as ethyl and methyl alcohols.

Since magnesium in the form of its alloys with other metals, as well as elemental magnesium, is suitable for the practice of this invention, the use of the term magnesium is intended to include both elemental magnesium and magnesium alloys. However, it is preferred to use elemental magnesium such as metallic magnesium turnings.

Preferred operating temperatures for this process are those lying between 25 and C. How

ever, temperatures in the range of 0 to 225 C. can be used.

The reaction can be carried out in the presence or absence of a volatile organic solvent, such as benzene, diethyl ether, toluene and aliphatic hydrocarbons. Generally it is preierred to operate unless otherwise specified.

9 'completel in the resenceof an organic solvent because this makes reaction easier.

The proportions of ingredients used in the process of this invention should always be ad- .iusted so that about one. equivalentof hydrogen to be present for each reducedproduct which in the case of .acrylonitrile Although it is prethe mixture of alpha,

is hexamethylenediamine. ferred to add the alcohol to bet'a ethylenically unsaturated aliphatic mononitrile and elemental magnesium, this procedure can be varied by adding. the elemental magnesium to the mixture of alcohol and nitrile.

The invention is further illustrated by the following example, in which parts areby weight Example A mixture of parts of mercuric chloride and 106 parts of acrylonitrile was placed in a flask and stirred at room temperature until solution was This solution was added to a mixture of 160 parts of dry benzene and 15 parts of mag nesium turnings and refluxed with stirring for one hour. At the end or this time, 35 parts of methyl alcohol was added over a periodof 1.5 hours, the resulting reaction mixture allowed to stand overnight, and then treated with 98 parts of concentrated sulfuric acid dissolved in 300 parts of water. The benzene washed in turn with 50 parts of water, 50 parts of; 10% sodium carbonate solution, and 50 parts of water. After removal of the benzene, distillation of the residue gave 6.4 parts crude adiponitrile boiling at 118F128 C./3.5 mm.

The adip'onitrile was identified :by conversion to adipic acid as follows: Hydrolysis of the fraction boiling at 118-128 C./3.5 mm. was carried out by boiling in parts of concentrated hydrochloric acid for one hour. The crude adipic acid which precipitated on cooling was recrystallized from 50 parts of water to yield 2.2 parts 01' adipic acid; M. P. 149-150 C. (M. P. of an authentic adipic acidsample was 150.5-l5l.5 C.) The mixedmelting point of the above product with the authentic sample of adipic acid was 149.5- 160.5 C.

A second run was carried out exactly as described above with the exception that the final reaction mixture was refluxed for 20 hours after the addition of methanol. In this run 3.2 parts of adipic acid, melting at 149.5-151 C., was obtained upon'hydrolysis of the .adiponitrile obtained.

Although the invention has been illustrated with respect to acrylonitrile specifically, it is to be understood that the process of this invention is generally applicable to alpha, betaethylenically unsaturated aliphatic mononitriles. Examples of such nitriles, besides acrylonitrile, are methacrylonitrile, alpha-ethylacrylonitrile, alpha-propylacrylonitrile, crotonitrile, and the like.

Lower primary aliphatic monohydric alcohols useful in the practice of this invention are methanol, ethanol, propanol, butanol and pentanol. It is preferred to use methyl or ethyl alcohol in this invention because of their availunder certain condilayer was separated,

- This invention is of particular value as a route to adiponitrile for conversion to adipic acid and hexamethylenediamine which are nylon intermediates. In addition, adiponitrile is of considerable interestas an intermediate for the synthesis of various otherorganic compounds.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that-I do not limit myself to the specific embodiments thereof except as defined in the appended claims. I

61 claim:

1. Aprocess for the simultaneous dimerization and reduction of acrylonitrile to adiponitrile which comprises treating acrylon trile in the presense of magnesium and mercuric chloride with active hydrogen produced by the reaction of said' magnesium with a primary aliphatic monohydric alcohol.

2. A process for the simultaneous dimerization and reduction of acrylonitrile to adiponitrile which comprises treating acrylonitrile in an inert volatile organic solvent and in the presence of magnesium and mercuric chloride with active hydrogen produced by the reaction of said magnesium with a primary aliphatic monohydric alcohol containing not more than five'carbon atoms.

3. .A process for the simultaneous dimerization and reduction of acrylonitrile to adiponltrile which comprises treating acrylonitrile in benzene and in the presence of magnesium and mercuric chloride with active hydrogen produced by the reaction of said magnesium with methanol.

4. A process for the simultaneous dimerization and reduction of an acrylonitrile containing from 3 to 6 carbon atoms to a saturated aliphatic dinitrile which comprises treating said acrylonitrile in the presence of magnesium and a promoter with active hydrogen produced by the reaction of said magnesium witha primary aliphatic monohydric alcohol.

5. A process for the simultaneous dimerization and reduction of an acrylonitrile containing from ,3 to 6 carbon atoms to a saturated aliphatic dinitrile which comprises treating said acrylonitrile in an inert volatile organic solvent and in the presence of magnesium and mercuric chloride with active hydrogen produced by the reaction of said magnesium with a primary aliphatic monohydric alcohol containing not more than five carbon atoms.

6. A process for the simultaneous dimerization and reduction of acrylonitrile containing from 3 to 6- carbon atoms to a saturat d aliphatic dinitrile which comprises treating said acrylonitrile in benzene and in the presence of magwith magnesium to liberate active hydrogen.

nesium and mercuric chloride with active hydrogen produced by the reaction of said magnesium with methanol.

ROBERT M. LEEKLEY.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Winans Nov. 9, 1943 

